A Review of the Yanshanian ore-related felsic magmatism and tectonic settings in the Nanling W-Sn and Wuyi Au-Cu metallogenic belts, Cathaysia Block, South China

Abstract The Cathaysia Block in South China is characterized by extensive Yanshanian felsic magmatism and related large-scale W-Sn-Au-Cu polymetallic mineralization. The Nanling area, a large granite province in the western Cathaysia Block, represents the largest W–Sn metallogenic province in the world. By contrast, the Wuyi area in the eastern Cathaysia Block is characterized by volcanic-subvolcanic rocks associated with porphyry-epithermal Au-Cu mineralization. We summarize the published reliable rock-forming and ore-forming dating data, petrogeochemistry, zircon Hf isotopes, Re contents in molybdenite, and He-Ar isotopes of fluid inclusions in ore minerals to better understand the ore-related magmatism and corresponding metallogenic settings in these two contrasting metallogenic belts. Multiple cycles of W-Sn mineralization occurred from Neoproterozoic to Cretaceous in the Nanling area. The Yanshanian W-Sn mineralization related granites were primarily emplaced during Late Jurassic (160–150 Ma). Geochemically, these granites generally belong to highly fractionated granite, with high SiO2 and K2O contents, and ‘V-shape’ rare earth elements (REE) patterns. The lack of arc volcanic rocks and the widespread presence of highly fractionated granites in the Nanling area is likely consistent with the intra-continental extensional setting in response to the far-field effects of subduction of the paleo-Pacific plate. In addition, W-Sn mineralization related granites in the Nanling area have low epsilon Hf isotopic values, together with low Re contents in molybdenite and low Ra values for He-Ar isotopes of sulfide minerals, suggesting that they were principally derived from crustal materials, with few involvements of mantle materials. The Yanshanian volcanic-subvolcanic rocks in the Wuyi area share similar geochemical features with typical arc magmatism, such as the enrichment in large ion lithophile elements (LILEs), and the depletion in high field strength elements (HFSEs, Nb, Ta and Ti). The Middle-Late Jurassic (165-150 Ma) Au-Cu mineralization is related to initial subduction of the paleo-Pacific plate, whereas the late Early Cretaceous to early Late Cretaceous (110-90 Ma) Au-Cu mineralization is linked to retreat of the subducted slab. The high Mg# and relatively higher zircon eHf(t) values suggest that metasomatized mantle was incorporated into ore related volcanic-subvolcanic rocks. Moreover, the relatively high Re contents in molybdenite and high Ra values for He-Ar isotopes of sulfide minerals support a significant contribution from the mantle to the Au-Cu mineralization in the Wuyi area. To sum up, we tentatively suggest a two-stage model to explain the spatio-temporal distribution of the ore-related granites and volcanic-subvolcanic rocks in the Nanling W-Sn and Wuyi Au-Cu metallogenic belts, respectively. The initial subduction of the paleo-Pacific plate produced volcanic arc rocks and related Au-Cu mineralization along the margin of the Cathaysia Block during 165-150 Ma, followed by the intra-plate extensional granite association and related W-Sn mineralization in the interior of the Cathaysia Block during 160-150 Ma. Late stage Au-Cu mineralization in the Wuyi belt is formed by remelting of metasomatized mantle wedge in a back-arc setting during 110-90 Ma in response to rollback of the paleo-Pacific plate.